As current applications associated with a multimedia image rapidly develops, various operating techniques, e.g., image compression, image encoding, image encryption and image matching, become mature to meet with user requirements of a large amount of image transmission, image conservation and image broadcasting.
Most video encoding techniques are based on the Joint Photographic Experts Groups (JPEG) standard, which is one of most common static image compression standards. Generally, the JPEG standard is a block-based static image processing technique for dividing an image into a plurality of non-overlapping blocks, each of which is to be converted and encoded. The block-based image compression technique is widely applied to multimedia video encoding processing. An operating principle of a dynamic image processing technique, e.g., the Moving Picture Exerts Group (MPEG) standard applied to image compression, also implements the image processing technique similar to the block-based JPEG standard.
Current image compression methods with the block-based MPEG standard are frequently applied to various types of network video transmission, digital televisions (TV) or video discs. However, when errors occur in decompressing or decoding a dynamic image or a static image that is stored or transmitted after being processed with the block-based video compression technique, image distortion may be created.
For example, when a user wishes to play a video disc via a multimedia player (e.g., a DVD player), a decoder of the DVD player inversely decompresses compressed videos from the video disc based on blocks, and the decompressed blocks are arranged to form a complete image frame. However, during the decompression, when distortion occurs in calculation of the decoder of multimedia player, the videos displayed on a screen or a liquid crystal display (LCD) TV may comprise unsmooth edges between blocks of the image frame, such that a frame viewed by an observer may comprise block noises, which is often called “blocking effect”.
Generally, the conventional screen or LCD TV passively receives and plays the decompressed image signal generated by the DVD player, without knowing positions of the block edges implemented when the decoder of the DVD player decompresses the image.
In order to reduce the foregoing blocking effect of the image, a current display device mainly adopts a de-blocking filter technique to remove or smooth the block noises. During the process of reducing the blocking effect, when all of the pixels of the image are processed by the de-blocking filter, efficiency of the processing is very low causing frame distortion of other normal areas of the image.
In order to solve the foregoing problem, the present invention provides a block-edge detecting method and an associated device capable of determining in advance block edges of an image to more effectively and more accurately remove block noises.